Automatic slack adjuster for brakes on railway cars and the like



June 3Q, 1.931. BRQWALL 1 811 914 AUTOMATIC SLACK ADJUSTER FOR BRAKES 0NRAILWAY CABS AND THE LIKE Filed May 13,, 1930 I5 Sheets-Sheet l lNver Ta/4 June 30, 1931. B. H. BROWALL AUTOMATIC SLACK ADJUSTER FOR BRAKES ONRAILWAY CARS AND THE LIKE Filed may 13, 1950 5 Sheets-Sheet 2 June 30,1931. B. 1-1. BROWALL.

AUTOMATIC SLACK ADJUSTER FOR BRAKES ON RAILWAY CARS AND THE LIKE Fil edMay 13, 1930 5 Sheets-Sheet 3 Patented June 30, 1931 UNITED STATESPATENT OFFICE BERT HENRY BROWALL, OF MALMO, SXVEDEN, ASSIGNO'R TOSV-ENSKA. AKTIELBOLAGET BROMSREGULATOB, OF MALMO, SWEDEN, A CORPORATIONOF SWEDEN AUTOMATIC SLACK ADJ USTEB FOR BRAKES ON RAILWAY CARS AND THELIKE Application filed May 13, 1930, Serial No. 452,088, and in GermanyJune 24, 1929 The subject of my present invention is a slack adjusterfor brakes on railway cars and the like for the purpose not-only toperform a reduction but also, when required, an increase of the slacksbetween the brake shoes and the wheels, and the invention refers toslack adjusters of the type which embodies two actuating mechanisms, oneof which is adapted for the increase, the other for the reduction of theslacks.

The characteristic of the invention is to be found therein that theactuating mechanism adapted for increase of the slacks is arranged insuch a manner that it performs a certain amount of increase of the slackfor each braking operation independent of the actual amountof slack thenat hand, and the actuating mechanism adapted for 7 reduction of theslacks is arranged in such a manner that it becomes effective only afterthat the source of braking power has performed alength of movementexceeding a predetere mined value, so thatby such means the increase ofthe slack performed by the slack increasing mechanism is'wholly or inpart eliminated, or even exceeded, whereby the result will be areduction of the slacks. Hence, the variation of the slack is the resultof-the difference between the effects of the two actuating mechanisms,and if the slack has itsnormal value, the effects of such mechanismswill be equal and thus eliminate each other.

In the following, the invention is to be explained by reference to theaccompanyingdrawings whichshow some different embodiments thereof. 7

Fig. 1 showsone embodiment of the apparatus seen in longitudinalsection,and.

Fig. 2 shows a cross sectional View of the same.

In the same manner Fig. 8 shows a second embodiment of the inventionseen'in longitudinal section, and

Fig. Lshows across sectional view of the latter.

Fig. 5 shows a cross section of a third em bodiment of the invention,and

Fig. 6 shows a longitudinal section of the same.

F ig. 7 shows a fourth embodiment of in ve-ntion seen in cross section,and V Fig. 8 is a diagrammatical elevation drawn to a smaller scale andshowing'the apparatus according to Fig. 7 mounted in its connection withthe brake cylinder structure.

In all ofthe embodiments according to the Figures 1 4 and 7 it isassumed that the variation of the slack is. to-be performed by means ofa nut and screw connection known per se, and wherein the nut is supposedto be connected with a rotatable part of construction of the slackadjuster (the pitch of the nut and screw connection being chosen in sucha manner that the connection is selflocking). The embodiment accordingto Figs. 5 and 6 is somewhat different in that the variation of theslack is adapted to be performed by means of a toothed rack which isdirectly slideable in its direction of length and acted upon by atoothed wheel adapted to be rotated by the slack adjuster and positioned in mesh with said toothed rack.

In the embodiment according to Figs. 1 and 2, the part of constructionadapted to be rotated by the apparatus: consists of a sleeveshaped ortubular rod 1 connected with a nut (not shown in the drawings), such nutin the common manner, at its rotatiombeing adapt- 7 ed to cause an axialdisplacement of another rod provided with corresponding threads, as

by such means to provide for a variation of the inter-distance betweenthe ends of the brake rigging rod, in which the apparatus is mounted. Ina manner known per se, the movement is alsotransmittedto the'apparatusby means of a crank member 2 affixed to a housing 3 enclosing the partsof the apparatus, such housing 3 being rotatably mounted around the axisof the rod 1. At its one end the said rod is rigidly connected witha pin4, which is rotatably mounted in the connection eye member 6 togetherwith the head 5, although said pin is prevented from axial displacementin any substantial degree, the head 5 serving the purpose of taking upthe stress arising when braking. Two pawls 7 and 8 respectively arehingedly mounted within the housing 3 onfixedipivot pins therein, thefirst mentioned pawl 7 serving as an actuating member for the purpose oflncreasing the slack, and the second mentioned pawl 8 serving asactuating member for reduction of the same. Both of the pawls arespring-actuated so as permanently to tend to engage a ratchet wheel 9fixed to the rod member 1 or to the pin l. The pawl 7 is provided with alaterally extending lug 10 adapted for coaction with a cam disc 11fixedly mounted in the connection eye, and the pawl S is provided with asimilar lug 12 for coaction with a cam disc 13, which is nor mallyrigidly connected with the connection eye but carried by a sleeve 14rotatably mounted on the connection eye and coacting with a set screw orthe like so thatit may be locked in different positions, and thereby itis possible to adjust the relative position of the cam 13 in relation tothe lug 12 on the pawl 8, so that the normal value of the slack may bevaried according to will.

In order to understand the manner of action of the apparatus it may beassumed that the crank 2, from the original position shown in Fig. 2, isrocked in a clock-wise direction when braking,so as by releasing thebrake to be rocked back again into said orig inal position, and themeans for performing such rocking movements of the crank may beconstructed in a manner known per se.

If starting from the original positions of the parts shown in Fig. 2,the pawl 7, when rocking the crank in a clockwise direction (whenbraking), will turn the ratchet wheel 9 a small angle before the lug 1Ostrikes the cam 11 and thereby lifts the pawl 7 out of engagement withthe ratchet wheel. The ratchet wheel 9, a d hereby also the tubular rodmember 1 will thus be given a certain rotation corresponding to anincrease of the slack with a certain amount. At the continuation of thebraking, the manner of action of the apparatus will be dependent on thelength of stroke of the source of braking power. If such stroke is toosmall, the crank :2 will not be turned so far that the lug 12 leaves thecam 13, and consequently the pawl 8 will then never come into engagementwith the ratchet wheel 9. When releasing the brake again, the parts ofconstruction will return to their positions shown in the drawings andthe result of the action will thus be an increase of the slack performedby means of ti e pawl 7. This manner of action will be repeated at eachbraking, until the said stroke has reached its normal value.

If the stroke is normal, the pawl 8 will be moved beyond the cam 13 toan equal extent as the pawl 7 takes a position in advance of the cam 11when the brake is released. Consequently the pawl 7 will increase theamount of slack with a certain value when braking,

but when the brake is released the increase of slack will be eliminatedagain by the pawl 8 previous to the disengagement of said pawl by meansof the cam 13, and therefore the slack will be withheld at its originalvalue.

If the stroke is too large, an increase of the slack will neverthelessbe performed when braking by means of the pawl 7 in the manner describedabove, but the crank 2 will then be rocked so far, that the pawl 8 hasbeen moved a greater angle beyond the cam 13. At the release of thebrake, the slack will consequently be reduced with an amount that isgreater than the increase of slack performed by the pawl 7, and theresult will be that a reduction of slack is performed answering to thedifference bet-ween the amount of work performed by the two pawls.

As the cam 13 is adjustable in peripheral direction by turning andlocking of the sleeve ll in a different position, the normal value ofthe working stroke, at which the work .erformed by one pawl iseliminated by the other, may be varied, and in this manner it ispossible to adjust the apparatus according to any desired value of theworking stroke.

In relation to the construction, the embodiment according to Figs. 3 and4 is generally the same as that according to Figs. 1 and 2, and the samereferences are used on corresponding parts of construction.

The difference is to be found therein, that the two pawls are'arrangedin such a manner that the reduction of the slack is performed whenbraking, the increase of the same being performed when releasing thebrake. This construction involves the advantage, that the braking stressarising when the brake shoes are in contact with the wheel rims in asimple manner may be utilized for the purpose of limiting the action ofthe apparatus at the reduction of the slack, so that the effect of theapparatus will onl be dependent on that part of the stroke of the sourceof brake power, the length of which corresponds to the amount of slackactually at hand, that part of the stroke, however, which is dependenton deformations in the brake rigging due to elasticity, or othermovements perhaps occurring due to the stresses, being without influenceon the result of the adjustment. For such purpose an elastic orresilient member, in a manner known per so, can be mounted for instancein the transmission means adapted for causing the movement of the crank,so that such resilient member accumulates the continued actuatingmovement appearing after that the stress .has arisen and the ratchetwheel cannot be further rotated due to the same.

Another difference is to be found therein 7 llb period of working of thepawl 7 Hereby a manua-l adjustinent of the slack is facilitated, and thetube 1 can be rotated both directions without the necessity of firstdisengaging the pawls fromthe ratchet wheel.

In order to understand the manner of actionof the apparatus, it mustbeassumed that the crank 2 in Fig. 4, when braking, is rocked a certainangle in a counter-clockwise direction, and when releasing the brake itis rocked a corresponding angle in the opposite direction. hen braking,both of the pawls will at first run idle for a certain angle. If theslack is too small, a locking stress will arise in the apparatus beforethe pawl 8, or itslug 12, has slid off from the cam 13, and consequentlysuch pawl will not perform any amount of work. The pawl 7 continues'insliding back over the cam 11, over the recess 11 and perhaps alsoupagain on the cam. hen thecrank 2, at the release of the brake, is rockedback again as described above, the pawl? will consequently perform anincrease of the slack corresponding to the peripheral length of therece'ss11 If the slack is normal, the pawl 8, when braking, will slidedown from the cam 13 and is moved a certain angle furthercorrespondingto the peripheral length of the recess 11 and thereby itperformsa. reduction of the slack, Hereby'the pawl 7 will, however,slide back past the recess 11 and when it is returned into its originalposition at the release of the brake, it will perform an increase of theslack corresponding to the length of the recess 11-, and therefore theactions of the two pawls will eliminate each other so that the slackwill finally remain unaltered. hen the slack is too large, the pawl 8will pass a rather great angle beyond the'end of the cam 13, and it willperforma reduction of the slack, which is considerably greater thantheiconstant increase of the same performed by the pawl 7 at the brakerelease, as the amount of said increase can never exceed a valuecorresponding to the length of the recess 11 i I Also in thisembodimentit will be possible, by adjustment of the position of the cam '13, tovary the moment at which the 'pawl 8 goes into engagement, and therebyalso to vary the amount of normal slack, same as in the embodiment'according to Figs. 1 and 2 andin I both embodiments it is the differencebetween the constant value of the increase of slack and the changeablevalue of the reduction of slack, which performs'theadjustment of theactual amount of slack. V

The embodiment according to Figs. '5 and 6 is based on the sameprinciples as those described above but applied to anothertype ofapparatus, in whichthe variation of the length of the pull rod, inwhich'the apparatus is mounted, is performed by'a direct sliding movment of the rod parts without relative rotation of the same. V I

' Inthis instance, the rod part or member 15 is vshaped into a toothedrack which is telescopically 'slidable in the other red part or member16 which is sleeve-shaped. A housing 17 is aflixed to the rod member 16,such housing forming bearings for a shaft 18 carrying a toothed wheel 19positioned in mesh with the aforesaid toothed rack. That part of theshaft 18 directly carrying the toothed wheel 19 is provided with threads18 the hub portion of the toothed wheel forming a nut on said threads.The crank 2 is carried by a sleeve 20 freely rotatab-ly mounted on theshaft 18, such sleeve being rigidly connected with two arms supporting'thepawls 7 and 8 respectively, the pawls acting in opposite directionsand coacting with a ratchet wheel 23 fiXed on the shaft 18. Be-

sides, a locking pawl 24 is 'hingedly mounted on a fixed pin in thehousing17, this locking. pawl acting in the same direction as theactuating pawl 8 and coactin'g' with a toothed locking wheel 25 freelyrotatably mounted on the shaft 18. The shaft 18 isprovided with anabutment or collar 26 forming an axial supporting face for the ratchetwheel 23 and the locking wheel'25 at one side, the nutshaped toothedwheel 19'being provided with a friction flange 27 supporting the lockingwheel 25 at the opposite side. A guide flange 28 is provided within thehousing 17, andthe pawls 7 and 8 are each provided with a latreleasingthe brake,it is rockedback the same anglein opposite'direction. WVhenbraking, the crank 2 by means of the pawl 7 will rotate the ratchetwheel 23a small angle, until the pawl is disengaged by the guide flange'28. At this small rotation of the ratchet'wheel 23, theshaft 18 willalso be rotated,'and the screw 18 forming part thereof is screwed outfrointhe nut-shaped wheel 19. As the ratchet wheel 23 and the lockingwheel 25 cannot be axially displaced towards the right in Fig. 5, thewheel-nut 19 must consequently be displaced towards the left, and herebythe contact pressure between the friction disc 27 and the wheel 25 willbe relieved, whereupon the rod 15, due to the stress arising whenbraking, may be pulled a certain amount tojwards the left in Fig.6, i.e. the slack is increased toa certain extent. Thetlispljacement oftherod 15 just described will, howerally extending lug for coaction withsaid ever, perform a corresponding rotation of the wheel-nut 19 in sucha direction, that the latter will again be axially displaced towards theright, and will be jammed against the locking wheel 25 due to the actionof the friction disc 27 and since the said wheel is locked by the pawl24, the pulling out of the rod 15 will cease. This functioning willcontinue until the pawl 7 is disengaged by the guide flange 28, so thatit cannot longer rotate the shaft 18, and consequently it can neitherdisconnect the wheel 19 for a further increase of the slack, asdescribed above. At the continuation of the braking, the crank 2 isfurther rotated in a clockwise direction according to Fig. 6, so thatthe pawl 8 will finally slide off from the guide flange and go intoengagement with the ratchet wheel a greater or smaller angle beyond theend of the guide flange 28, and thereafter the pawl 8, when releasingthe brake, will move in opposite direction to that referred to above, soas thereby, to a. greater or smaller extent, to eliminate the increaseof slack caused by the pawl 7. The locking wheel 2-5, which hereby musttake part in the said movement, is not locked in this direction by thepawl 24.

If the slack is too small, the pawl 8 will not move beyond the guideflange, and consequently the increase of slack performed by the pawl 7will be withheld. If the slack is normal, the pawl 8 will just move sofar beyond the guide flange 28 as required for eliminating the increaseof slack performed by the pawl 7, and hereby the slack is again reducedto the same amount as the increase of the same performed by the pawl 7On the contrary, if the slack is too large, the pawl 8 will move stillfurther beyond the guide flange 28, and it will reduce the slack agreater extent than the increase of the same by means of the pawl 7, theactual reduction of the slack being then equal to the difference betweenthe amounts of work performed by the two actuating pawls. Hence, it willbe seen that the manner of action of this apparatus in point ofprinciple is in conformity with the manner of action of the embodimentaccording to Figs. 1 and 2, and by the addition of a resilient member itmay naturally also be converted so as to correspond to the embodimentaccording to Figs. 3 and 1.

In point of principle, the embodiment according to Figs. 7 and 8 acts inthe same manner as that according to Figs. 3 and 4, although byinfluence from air pressure. will be seen from Fig. 8, the brakecylinder 29 is combined with two compressed air cylinders 30 and 31, thecylinder 30 of which being shorter than the other and directly connectedwith the cylinder cover by means of a pipe 32, the other cylinder 31being longer and connected with the cylinder 29 by means of a pipe 33 ata point between the ends of said cylinder, this point corresponding tors1r914 the length of stroke normally to be travellex by the brakepiston for the purpose of advancing the brake shoes towards the wheels,under the provision that the slack is normal. This point may naturallybe chosen according to the desired amount of normal slack, .and bysuit-able means it may also be adjustable so as to vary the location ofthe same. The slack adjuster can be supposed to consist of a screw 34:provided with a connection means for the brake lever, the osition ofsuch connection means being varia le (see Fig. 8), and then the saidconnection means may be given the shape of a nut mounted on the saidscrew, so that it is displaceable in the direction of length of thescrew by means of a relative rotation. Besides, the screw is alsoprovided with a ratchet wheel 35 (Fig. 7) fixed thereto and preferablysurrounded by a housing 36 combined with the cylinder structure 30,31.The cylinder 30 is provided with a reciprocable piston 37, the pistonrod of which is hingedly connected with a pawl 38 adapted for coactionwith the ratchet wheel 35, and the cylinder 31 in a similar manner isprovided with a piston 39 connected with another pawl 40 .adapted forcoaction with said ratchet wheel, the housing 36 being interiorlyprovided with an abutment face 41, which by coaction with a lug 4C2 onthe pawl 38 performs a disengagement of the said pawl after a certain.amount of displacement of the same. Both of the pistons are acted uponby return springs tending normally to keep them in the positions shownin Fig. 7, and the pawl 38 may be in engagement with the ratchet wheel35, when the brake is release-d, but the pawl 4L0 being then out ofengagement therewith. Finally it is to be assumed, that the pitch of thescrew is chosen in such amanner, that it is self-locking.

The manner of action is as follows 2- Y'Vhen braking, a pressure will atonce be transplanted to the cylinder 30, and the pawl 38 rotates theratchet wheel 35 and the screw 34 for the purpose of performing acertain amount of increase of the slack, until the pawl is disengaged bymeans of the abutment face. As long as the slack is so small, that thepiston within the brake cylinder 29 does not arrive in the positionrequired for connection of the pipe 33, no compressed air will beintroduced into the cylinder 31, and consequently the increase of slackperformed by the piston 37 will be maintained. In case A the slack isnormal, the piston within the brake cylinder 29 will arrive at theposition just required for connect-ion of the pipe 33, whereby thepiston 39 will come into action and by means of the pawl 40 it willrotate the ratchet wheel 35 and the screw 34: the same amount back asthe rotation caused by the pawl 38. This being performed, the brakerigging (due to the normal value of the slack) will be set under sogreat a stress that the piston 39 cannot rotate the ratchet wheel 35 anyfurther, and the continued braking will cause an increase of pressurewithin the cylinder 31 only, such increase of pressure acting in thesame manner as the resilient member described above and adapted formounting in the transmission means connected with the crank 2. In casethe slack is too large, the brake piston will also travel past the pointof connection of the pipe 33, but on account of the amount of slack thebraking stress will not arise so early, and the piston 39 is able torotate the ratchet wheel 35 still further, and since the piston 39 has agreater length of stroke than the piston 37, the former will perform agreater reduction of the slack than the increase of the same performedby the latter, before the braking stress has increased to such'a valuethat it prevents the further rotation of the ratchet wheel 35.

What I claim and desire to secure by Let-- ters Patent is 1. In anautomatic slack adjuster of the character described, an actuating meansadapted to actuate the slack adjuster in a direction for increasing theslack, another actuating means adapted for actuation of the adjuster inan opposite direction for reduction of the slack, the said two actuatingmeans being arranged independent of each other in such a manner thatboth of them 7 and adapted to actuate the adjuster in an op-.

posite direction for reduction of the slack, means adapted for causingboth of said actuating means to actuate the slack adjuster when braking,so that the result will be dependent on the difference between theactuations thus performed, and guide means combined with at least one ofthe actuating means and adapted for controlling the moment and durationof the actuation of said means.

4. In an automatic slack adjuster according to claim 3, the additionalfeature that the guide means are adjustably mounted and adapted tocontrol the effect of the adjust ment desired.

5. In an automatic slack adjuster of the character described, anactuating means adapted to actuate the slack adjuster in a direction forincreasing the slack, a driving means for such actuating means, anotheractuating means independent of the former and adapted to actuate theadjuster in an opposite direction for reduction of the slack, a seconddriving means for such other actuating means and independent of thefirst mentioned driving means, means adapted for causing both of theaforesaid actuating means to actuate the slack adjuster when braking, sothat the result will be dependent on the difference between theactuations thus performed, and means adapted to disengage each of theactuating means after performance of its actuation.

In testimony whereof I have signed my name to this specification.

BERT HENRY BROWVALL.

